120 



MANUAL OF BOTANY 



The advance in histological differentiation which marks the 

 gametophyte is also seen in the structure of the sporophyte. 

 There is a well-marked epidermis furnished with rudimentary 

 stomata. The seta contains a strand of pseudo- vascular tissue 

 similar to that described as occurring in the stem. The tissue 

 of the sporogonium also contains chloroplastids. 



The phenomenon of a])0si)07'y, which is not uncommon in 



Ci 



6 



the next group, the Pteridophyta, occurs also in some mosses. 

 Under favourable conditions some of the cells of the sporogonium 

 put out protonemal filaments which give rise by budding to 

 new gametophytes. We get thus the formation of the latter 

 from the sporophyte without the production of spores. This 

 may be taken as a case of vegetative reproduction, which we 

 have seen to be so common in the gametophyte generation. 



